It was made up of a total of 1,427 coins, dating from the 19th century, which were never used, experts said, and is believed to be the largest treasure find ever in the United States.

It's reported to be the biggest ever treasure find on US soil

The couple were walking their dog when they found the coins, Sky News said.

David Hall, co-founder of Professional Coin Grading Service, which authenticated the find, said: "I don't like to say once-in-a-lifetime for anything, but you don't get an opportunity to handle this kind of material, a treasure like this, ever.

"We've seen shipwrecks in the past where thousands of gold coins were found in very high grade, but a buried treasure of this sort is unheard of," David McCarthy of currency firm Kagin's, who is advising the couple, told Reuters.

"I've never seen this face value in North America and you never see coins in the condition we have here."

The couple plan to keep some of the coins, and sell others on Amazon, with some proceeds going to charity, it was reported.